In electrophotographic applications such as xerography, a charge retentive surface is electrostatically charged, and exposed to a light pattern of an original image to be reproduced to selectively discharge the surface in accordance therewith. The resulting pattern of charged and discharged areas on that surface form an electrostatic charge pattern (an electrostatic latent image) conforming to the original image. The latent image is developed by contacting it with a finely divided electrostatically attractable powder referred to as "toner". Toner is held on the image areas by the electrostatic charge on the surface. Thus, a toner image is produced in conformity with a light image of the original being reproduced. The toner image may then be transferred to a substrate (e.g., paper), and the image affixed thereto to form a permanent record of the image to be reproduced. Subsequent to development, excess toner left on the charge retentive surface is cleaned form the surface. The process is well known, and useful for light lens copying from an original, and printing applications from electronically generated or stored originals, where a charged surface may be imagewise discharged in a variety of ways.
Although a preponderance of the toner forming the image is transferred to the paper during transfer, some toner invariably remains on the charge retentive surface, it being held thereto by relatively high electrostatic and/or mechanical forces. Additionally, paper fibers, Kaolin and other debris have a tendency to be attracted to the charge retentive surface. It is essential for optimum operation that the toner remaining on the surface be cleaned thoroughly therefrom.
A commercially successful mode of cleaning employed in automatic xerography utilizes a brush with soft fiber bristles which have suitable triboelectric characteristics. While the bristles are soft they are sufficiently firm to remove residual toner particles from the charge retentive surface. In addition, webs or belts of soft fibrous or tacky materials and other cleaning systems are known.
More recent developments in the area of removing residual toner and debris from a charge retentive surface have resulted in cleaning structures which, in addition to relying on the physical contacting of the surface to be acted upon also rely on electrostatic fields established by electrically biasing one or more members in a cleaning system.
It has been found that establishing an electrostatic field between the charge retentive surface and the cleaning member such as a fiber brush or a magnetic brush enhances toner attraction to the cleaning brush surface. A biased detoning device may be used to remove toner from the cleaning member. Such arrangements are disclosed in U.S. Pat. No. 3,572,923 to Fisher, U.S. Pat. No. 3,655,373 to Fisher et al. U.S. Pat. Nos. 3,780,391 to Leenhouts, 3,580,673 to Yang and 3,722,018 to Fisher. The creation of the electrostatic field between the brush and photoreceptor is accomplished by applying a D.C. voltage to the brush. When the fibers or granules forming the brush are electrically conductive and a bias is applied thereto, cleaning is observed to be more efficient than if the fibers or granules are non-conductive or insulative.
EP No. 036290-B1 discloses a magnetic brush and insulative detoning roll both of which have electrical biases applied thereto for establishing the desired electrostatic fields between the brush and the photoreceptor and between the brush and the detoning roll. The field established between the conductive brush and the insulative photoreceptor is such that the toner on the photoreceptor is attracted to the brush. Thus, if the toner on the photoreceptor is positively charged, then the aforementioned field would be negative. In order to attract the toner from the brush onto the detoning roll, the detoning roll is electrically biased to a greater negative potential than the brush.
U.S. Pat. No. 4,494,863 to Laing discloses a toner removal device for removing residual toner and debris from a charge retentive surface after transfer of toner images from the surface. This device is characterized by the use of a pair of detoning rolls, one for removing toner from a biased cleaner brush and the other for removing debris such as paper fibers, Kaolin, etc., from the brush. The rolls are electrically biased so that one of them attracts toner from the brush while the other one attracts debris. Thus, the toner can be reused without degradation of copy quality while the debris can be discarded. U.S. Pat. No. 4,639,124 to Nye shows a similar arrangement separating colored toners collected from a magnetic brush. U.S. Pat. No. 4,116,555 to Young et al. similarly discloses a toner removal device characterized by the use of a pair of detoning rolls, one for removing toner from a biased magnetic cleaner brush and the other for removing wrong sign toner.
A blade cleaning arrangement for removal of toner from the detoning rolls is used in the Xerox 1075 and 1090 copiers. These products use 0.002 inch thick Starret steel shim stock as a scraper blade held in a channel with a plastic spring clip. When the blade requires replacement due to wear, the blade and auger channel assembly must be removed for the cleaner, the spring clip removed, the blade removed, the new blade inserted, the spring clip reinstalled and the assembly reinstalled in the cleaner. This is a time consuming operation, and difficult to perform. U.S. Pat. No. 4,083,633 to Shanly and U.S. Pat. No. 4,447,929 to Hennig et al show blade holders where the blade is held in position by its own resiliency and frictional engagement with the walls of the blade holder.
In the Xerox 1075 and 1090 copiers, the blade holder assembly contain the support structures of the auger tubes. The supports are in the form of aluminum extrusions that slide into recesses provided in the cleaner housing. These assemblies, including the auger tubes are removable for cleaning if required. If the cleaner was provided in a single extruded housing, desirable for cost and assembly benefits, it is possible that toner could collect between the auger tube, the holder around the auger and the cleaner extrusion. JP No. 57-198485 to Hida shows a cleaning device removable form a copying machine including a vessel in which accumulating toner collects and a seal which causes accumulating toner to drop into the vessel. U.S. Pat. No. 4,436,411 to Miyoshi et al shows a developing device in which a toner particle dispenser with a reciprocating slide plate to break up agglomerated masses moving along the side walls of the toner particle dispenser to prevent clogging.